Process for the deinking of coated paper or paperboard

ABSTRACT

A process for the deinking of a coated paper or paperboard is disclosed, the process comprises a step of providing a coating layer comprising a calcium- or magnesium-exchanged clay which is deposited on the paper or paperboard before the ink layer. In a further step said calcium- or magnesium-exchanged clay is activated and the paper is subsequently treated with water.

The present invention relates to a process for the deinking of coatedpaper or paperboard, which may be used for a multitude of inks, forexample digital printing inks, laser printing inks, offset inks,flexographic inks and/or rotogravure inks.

In Switzerland alone in 2012 the overall consumption for printed paperswas more than 700 000 tons (Source: homepage PAPIER SCHWEIZ). Even ifpaper is one of the renewable raw materials the recycling of paper isimportant for economic and environmental reasons. The efficient deinkingof the printed paper is one of the most challenging steps during therecycling process.

US 2012/0031573 A1 refers to a composition for deinking waste paper,wherein the composition comprises: a surfactant and a hydrophobickaolin-based deinking component.

U.S. Pat. No. 1,421,195 relates to a process for deinking paper whichconsists in subjecting the paper to an alkaline solution of bentonite.

WO 2010/147581 A1 refers to a process for deinking printed waste papercomprising the steps of: a) converting the printed waste paper to anaqueous pulp slurry in a pulper, where ink is detached from paper pulp,b) subjecting the pulp slurry to flotation in order to removehydrophobic contaminants including ink from the pulp slurry, saidflotation being carried out in the presence of a deinking chemicaladditive comprising modified silica obtained by treating hydrophilicsilica particles with a hydrophobic organic liquid.

EP 0 512 212 A relates to a process for deinking wastepaper, whichcomprises (a) contacting wastepaper with an aqueous system whichcontains an agent selected from the group consisting of: (i) a mixtureof one or more quaternary ammonium salts and one or more smectite-typeclays; and (ii) one or more organically modified smectite-type clays;and (b) recovering deinked paper pulp from the aqueous system. EP 0 572037 A1 refers to a coating pigment that can be fixed on printing mediawithout the use of organic binders comprising at least one waterswellable layer silicate in the amount of at least 30 weight percentbased on the weight of the pigment wherein said coating pigment has aswelling volume of about 5 to about 30 ml based on a suspension of 2 gof coating pigment in 100 ml water and wherein said water swellablelayer silicate has a zeta potential value of about −35 to about +10 mV.

WO 2013/123150 relates to a method for producing exfoliated clayplatelets from a swellable clay material, comprising: providing anexfoliating agent comprising an anionic extractant, and exposing theswellable clay material to the exfoliating agent, wherein theexfoliating agent produces exfoliated clay platelets from the swellableclay material.

WO 2007/081921 A2 refers to a method of deinking printed waste paperthat comprises ink and paper pulp, comprising the steps of: a)converting the printed waste paper to an aqueous pulp slurry in apulper; b) contacting said aqueous pulp slurry with an inorganicsubstrate; c) contacting said aqueous pulp slurry with a deinkingcomposition which comprises a nonionic surfactant, a fatty acid, or amixture thereof; d) separating said ink in the aqueous pulp slurry; ande) recovering deinked paper pulp from the aqueous pulp slurry; whereinsaid deinking composition is optionally mixed with said inorganicsubstrate prior to step (b).

DE 196 31 150 A1 relates to a process involving treatment of a beatensubstrate with aqueous caustic alkali, hydroxide peroxide, a surfactantand optionally water glass and separating the loosened printing ink byflotation, the surfactant used is an amphiphilic cationic surfactantwith a hydrophilic lipophilic balance value of 8 to 13, the causticalkali content is such that the pH does not exceed 9 and the water glasscontent is 0 to 0.5 wt.-%.

WO 2006/123996 refers to a process for deinking recycled fibrescomprising a) providing an aqueous pulp suspension containing recycledfibres, printing ink and calcium carbonate; b) stabilizing the hardnessof said pulp suspension by causing dissolution of calcium carbonatecontained in said suspension or in an aqueous fluid added to saidsuspension; and c) subjecting the resulting pulp suspension to flotationto separate said printing ink from said suspension.

DE 736450 relates to a process for producing coated papers using abinding medium and a pigmented coating composition, wherein bentonite ora similar swelling clay is used as a binder in the coating composition.

The article “Novel surface preparation concept for improved deinking:Bringing digital, functional and water-based prints into the mainstreamrecycling process” concerning the deinking of printed products bycoating paper with a specific exfoliation layer and further activationof said layer with sodium hydroxide causing the deinking was publishedin 2013 by Gane (Advances in Printing and Media Technology, Vol. XL,2013 Ed. Nils Enlund and Mladen Lovrecek, ISSN 2225-6067, ISBN978-3-9812704-4-0, 179-192.)

In view of the foregoing, the expert is still faced with the problem ofefficient, ubiquitous and environment-friendly deinking of coated paper.Still today, deinking processes have several disadvantages. For example,not all kinds of ink release easily from the surface of the paper intothe water, especially pigment inks adhere strong on the paper surface.Furthermore, for peeling the ink from the papers reagents are used thatmay disturb later purification steps, e.g. a strong base, like sodiumhydroxide, can deactivate pH sensitive cationic collector agents, likemodified polyethyleneimines. The activity of these collector agents isessential during a further purification by flotation.

There is still a need to provide deinking processes which may reduce oravoid one or more of the aforementioned technical drawbacks.

It is thus an object of the present invention to provide a process forthe deinking of coated paper or paperboard which is very flexibleconcerning the kind of inks. Another object may also be seen in theprovision of a more efficient process working under moderate conditions,for example with regard to the pH-value and allowing high flexibilityconcerning the methods and reagents for further purification of theink-containing aqueous phase obtained after the deinking.

One or more of the foregoing and other problems are solved by thesubject-matter as defined herein in the independent claims.

A first aspect of the present invention relates to a process for thedeinking of coated paper or paperboard, said process comprising thesteps of:

-   -   (i) providing a coated paper or paperboard comprising,        -   (a) at least one layer consisting of a coating composition            comprising,            -   (a1) a calcium- or magnesium-exchanged clay,            -   (a2) a binder,        -   (b) at least one layer having a thickness in the range from            0.1 to 10 μm comprising ink,    -   (ii) activating the calcium- or magnesium-exchanged clay before        or during step (iii) by,        -   (A) carrying out step (iii) with water comprising monovalent            ions selected from the group consisting of sodium, lithium,            potassium, ammonium and mixtures thereof, and/or        -   (B) providing in step (i) a binder (a2) that is soluble in            water and comprises monovalent ions selected from the group            consisting of sodium, lithium, potassium, ammonium and            mixtures thereof, and/or        -   (C) adding monovalent ions selected from the group            consisting of sodium, lithium, potassium, ammonium and            mixtures thereof in form of a salt before or during step            (iii),    -   (iii) treating the coated paper or paperboard as provided in        step (i) with water to obtain an aqueous suspension comprising        at least ink, clay particles and        -   a paper pulp or a paper residue, wherein layer (a) is            deposited on the paper or paperboard before layer (b).

The process of the present invention can comprise a further step (iv) ofseparating the paper or paper board from the aqueous suspension obtainedin step (iii). The present invention makes use of a calcium-exchangednanoclay which is selected from the group consisting of bentonite,smectite, montmorillonite and mixtures thereof and preferably isbentonite.

The activating step (ii) according to the present invention can be,

-   -   (A) carrying out step (iii) with water comprising an excess of        monovalent ions selected from the group consisting of sodium,        lithium, potassium, ammonium and mixtures thereof with respect        to calcium or magnesium ions, wherein sodium ions are preferred        and/or    -   (B) providing in step (i) a binder (a2) that is soluble in water        and comprises monovalent ions selected from the group consisting        of sodium, lithium, potassium, ammonium and mixtures thereof        with respect to calcium or magnesium ions, wherein sodium ions        are preferred and/or    -   (C) adding sodium ions in form of a salt selected from the group        consisting of sodium chloride, sodium nitrate, sodium sulphate,        sodium carbonate and/or mixtures thereof before or during step        (iii).

The binder can be water soluble and can be selected from the groupconsisting of starch, carboxymethylcellulose, and mixtures thereof andpreferably is carboxymethylcellulose, more preferably the water-solublebinder comprises an excess of sodium ions with respect to calcium ormagnesium ions and/or the coating composition can comprise anotherbinder which is water-dispersible, preferably a latex-binder.

The coated paper may comprise at least one layer (c) comprising 1 to 30g/m², preferably from 5 to 20 g/m² and more preferably 6 to 15 g/m² of acalcium carbonate-comprising material.

The calcium carbonate-comprising material can be selected from groundcalcium carbonate, precipitated calcium carbonate, surface-modifiedcalcium carbonate, or a mixture thereof, and preferably is a naturalground calcium carbonate. Furthermore, the calcium carbonate-comprisingmaterial may be selected from natural calcium carbonate sources andpreferably is selected from the group consisting of marble, limestone,chalk, dolomite, and mixtures thereof. The thickness of the at least oneink layer can be in the range from 0.75 to 5 μm and preferred in therange from 0.9 to 2.1 μm. The water applied in step (iii) may beselected from the list of tap water, deionized water and mixturesthereof, preferably is tap water, and more preferably is tap watercomprising sodium ions, even more preferably is tap water comprising anexcess of sodium ions with respect to calcium or magnesium ions.

During step (iii) of the process according to the present inventionscraping of the surface of the paper or paperboard may be carried out.The content of the calcium-exchanged nanoclay (a1) in the composition asprovided in step (i), may be in the range from 3 to 15 wt.-%, morepreferably 5 to 12 wt.-% and most preferably from 5 to 10 wt.-% based onthe total weight of the coating composition, and/or the coating weightof the at least one layer (a) is from 0.1 to 20 g/m², preferably 1 to 10g/m². The content of the water-soluble binder (a2) in the composition asprovided in step (i) may be in the range from 0.1 to 12 wt.-%, morepreferably from 0.2 to 5 wt.-%, even more preferably from 0.3 to 2.0wt.-% and most preferably from 0.5 to 1.5 wt.-% based on the solidsweight of the coating composition. The ink in layer (b) may be a digitalprinting ink selected from the group consisting of ink- or dye-basedinkjet inks, laser printing inks and/or toners, offset inks,flexographic inks, rotogravure inks and mixtures thereof.

The process of the present invention may further comprise the steps of

-   -   (v) transferring the aqueous suspensions as obtained in        step (iii) or (iv) to a flotation cell, and/or    -   (vi) adding at least one collector agent to the aqueous        suspensions as obtained in step (iii), (iv) or (v), and    -   (vii) passing a flotation gas into the aqueous suspension formed        in step (vi) to obtain a phase comprising water and a froth        comprising clay and ink, and    -   (viii) separating the froth as obtained in step (vii) from the        water.

The at least one collector agent may be selected from the groupconsisting of modified polyethyleneimines, active and hydrophobictensides, preferably xanthate or thio phosphates, alkyl sulphates,polyalkylenimines, primary amines, tertiary amines, quaternary amines,fatty amines, esterquats, polyesterquats, and imidazolines or quaternaryimidazolium compounds, preferably quaternary imidazolium methosulphates,and most preferred are polyethyleneimines. The content of the at leastone collector agent may be in the range from 0.001 to 50 wt.-% based onthe total weight of the solids in the aqueous suspension as provided instep (iii) or (iv), preferably from 0.002 to 20 wt.-% based on the totalweight of weight of the clay particles and optional other fillers, morepreferably in the range from 0.05 to 0.8 wt.-% based on the total weightof the weight of the solids in the aqueous suspension as provided instep (iii) or (iv) and most preferably in the range from 0.02 to 0.1wt.-%, based on the total weight of the weight of the solids in theaqueous suspension as provided in step (iii) or (iv).

It should be understood that for the purposes of the present invention,the following terms and expressions have the following meanings:

The term “deinking” in the meaning of the present invention refers tothe removal of ink from paper pulp to obtain deinked paper pulp, wherebythe paper pulp can be essentially free of ink e.g. <1 wt.-% ink remainson the paper pulp based on the starting content or the content of ink onthe pulp is at least significantly reduced, such as by 50 to 80 wt.-%based on the ink content before the deinking.

The expression “calcium-exchanged clay” refers to a clay which is ionexchangeable and is essentially exchanged with calcium ions, e.g. morethan 50%, preferably more than 90% of the cations are calcium ions.

The expression “water-soluble binder” in the meaning of the presentinvention refers to binders which are good water-soluble this means 10g, preferably 50 g binder can be solved in 1 litre water.

The expression “water-dispersible binder” in the meaning of the presentinvention refers to binders whereby the solids/colloidal material isdispersed in the water phase without phase separation and without asignificant (this means>30%) viscosity increase over a period of 3,preferably 7 days.

The term “latex” in the meaning of the present invention refers toaqueous dispersions of colloidal polymer particles. These particles mayhave a d₅₀ value in the range from 10 to 5 000 nm.

The term “filler” in the meaning of the present invention refers tosubstances which may be added to materials, such as polymers,elastomers, paints, or adhesives, e.g. to lower the consumption of moreexpensive materials or to improve material or mechanical properties ofthe resulting products. The person skilled in the art very well knowsthe fillers, typically mineral fillers, used in the respective field.

The expression “activating the calcium- or magnesium-exchanged clay” inthe gist of the present invention means at least partially exchangingthe calcium or magnesium ions with monovalent cations, preferably withsodium, and therewith transforming the clay at least partially into itswater-swellable form.

“Layer (b)” comprising ink according to the present invention may be asingle layer (solid tone) or when the ink has been applied as dots aseries of small dimension layers.

A “natural calcium carbonate source” may be any natural materialcomprising calcium carbonate. Such materials comprise, for example,marble, limestone, chalk, dolomite, and the like.

Throughout the present document, the “particle size” of an alkalineearth metal carbonate-comprising material, or other particulate materialis described by its distribution of particle sizes. The value d_(x)represents the diameter relative to which x % by weight of the particleshave diameters less than d_(x). This means that the d₂₀ value is theparticle size at which 20 wt.-% of all particles are smaller, and thed₉₈ value is the particle size at which 98 wt.-% of all particles aresmaller. The d₉₈ value is also designated as “top cut”. The d₅₀ value isthus the weight median particle size, i.e. 50 wt.-% of all grains arebigger and the remaining 50 wt.-% are smaller than this particle size.For the purpose of the present invention the particle size is specifiedas weight median particle size d₅₀ unless indicated otherwise. Fordetermining the weight median particle size d₅₀ value or the top cutparticle size d₉₈ value a Sedigraph 5100 or 5120 device from the companyMicromeritics, USA, can be used. The method and the instrument are knownto the skilled person and are commonly used to determine grain size offillers and pigments. The measurement is carried out in an aqueoussolution of 0.1 wt.-% Na₄P₂O₇. The samples are dispersed using a highspeed stirrer and supersonics.

Where an indefinite or definite article is used when referring to asingular noun, e.g., “a”, “an” or “the”, this includes a plural of thatnoun unless anything else is specifically stated.

Where the term “comprising” is used in the present description andclaims, it does not exclude other elements. For the purposes of thepresent invention, the term “consisting of” is considered to be apreferred embodiment of the term “comprising”. If hereinafter a group isdefined to comprise at least a certain number of embodiments, this isalso to be understood to disclose a group, which preferably consistsonly of these embodiments.

Terms like “obtainable” or “definable” and “obtained” or “defined” areused interchangeably. This, e.g., means that, unless the context clearlydictates otherwise, the term “obtained” does not mean to indicate that,e.g., an embodiment must be obtained by, e.g., the sequence of stepsfollowing the term “obtained” though such a limited understanding isalways included by the terms “obtained” or “defined” as a preferredembodiment.

The Coated Paper or Paperboard

According to step (i) of the process according to the present invention,a coated paper or paperboard is provided. Said coated paper orpaperboard is characterized by that it comprises at least two layers (a)and (b), whereby layer (a) consists of a coating composition and layer(b) has a thickness in the range from 0.1 to 10 μm and comprises ink.The coating composition of layer (a) comprises (a1) a calcium- ormagnesium exchanged clay and (a2) a binder.

In a preferred embodiment the coating composition of layer (a) comprises(a1) a calcium-exchanged clay, preferably a nanoclay, and (a2) awater-soluble binder.

In one embodiment the coated paper or paperboard has a weight in therange from 10 to 600 g/m², preferably 20 to 400 g/m². In anotherembodiment the coated paper has a weight in the range from 20 to 200g/m², preferably 40 to 200 g/m².

In one embodiment of the present invention the calcium-exchanged clay ofthe coating composition in layer (a) is a nanoclay selected from thegroup consisting of bentonite, smectite, montmorillonite and mixturesthereof and preferably is bentonite.

In one embodiment the content of the calcium exchanged clay (a1) in thecoating composition, is in the range from 3 to 15 wt.-%, more preferably5 to 12 wt.-% and most preferably from 5 to 10 wt.-% based on the totalweight of the coating composition. The total weight of the coatingcomposition encompasses the solids and water.

The calcium exchange of the clay (a1) can be carried out during thepreparation of the coating composition, e.g., by adding calciumhydroxide or calcium chloride, whereby calcium chloride is preferred.

Preferred binders in the coating composition in layer (a) arewater-soluble binders like starch, carboxymethylcellulose, or mixturesthereof whereby carboxymethylcellulose is most preferred. The coatingcomposition can also comprise water-dispersible binders like latex, andthe coating may comprise a mixture of water-soluble andwater-dispersible binders. According to another embodiment of thepresent invention the water-soluble binder comprises an excess ofmonovalent ions selected from the group consisting of sodium, lithium,potassium, ammonium and mixtures thereof with respect to calcium ormagnesium ions, wherein sodium ions are preferred. The excess of theseions with respect to calcium or magnesium ions is in the range from 1000:1 to 100 000:1.

In one embodiment the content of the binder (a2), preferably of awater-soluble binder, in the coating composition is in the range from0.1 to 12 wt.-%, more preferably from 0.2 to 5 wt.-%, even morepreferably from 0.3 to 2.0 wt.-% and most preferably from 0.5 to 1.5wt.-% based on the solids weight of the coating composition.

In one embodiment the coating composition in layer (a) comprisesbentonite and carboxymethylcellulose, preferably acarboxymethylcellulose having an excess of sodium ions with respect tocalcium ions. The sodium content of the carboxymethylcellulose may be inthe range from 1 to 40 wt.-% based on the overall weight of thecarboxymethylcellulose, preferably 5 to 15 wt.-% based on the overallweight of the carboxymethylcellulose.

Before bringing the coating composition as layer (a) onto the paper orpaperboard the composition comprises water, said water is evaporatedduring the coating process.

In another embodiment the coating composition in layer (a) compriseswater soluble calcium or magnesium salts, preferably calcium chloridefor carrying out the ion exchange of the clay in situ.

In one embodiment of the present invention the solids content of thecoating composition before coating layer (a) is in the range from 1 to60 wt.-%, preferably 2 to 20 wt.-% and more preferably 4 to 10 wt.-%.

In one embodiment according to the present invention the coating weightof layer (a) is in the range from 0.1 to 20 g/m², preferably from 1 to10 g/m².

The thickness of layer (b) is in the range from 0.1 to 10 μm, preferablyin the range from 0.75 to 5 μm and more preferably from 0.9 to 2.1 μm.

In one embodiment according to the present invention the coating weightof layer (b) is in the range from 0.5 to 20 g/m², preferably from 1 to10 g/m² and more preferably from 1.5 to 4 g/m².

In one embodiment of the present invention the ink in layer (b) is adigital printing ink selected from the group consisting of ink- ordye-based inkjet inks, laser printing inks and/or toners, offset inks,flexographic inks, rotogravure inks and mixtures thereof.

In another embodiment the ink is black, blue, red, cyan, magenta ordifferent inks with more than one of these colours are used.

The coated paper as provided in step (i) may comprise further layers. Inone preferred embodiment the coated paper comprises at least one furtherlayer (c) comprising a calcium carbonate-comprising material.

The coating weight of layer (c) is in one embodiment in the range from 1to 30 g/m², preferably from 5 to 20 g/m² and more preferably 6 to 15g/m². In another preferred embodiment layer (c) consists of a calciumcarbonate-comprising material.

Furthermore, the coated paper as provided in step (i) may have furtherlayers comprising a calcium carbonate-comprising material.

In one embodiment the calcium carbonate-comprising material is selectedfrom ground calcium carbonate, precipitated calcium carbonate,surface-modified calcium carbonate, or a mixture thereof, and preferablyis a natural ground calcium carbonate.

In some embodiments of the process according to the present invention,the calcium carbonate-comprising material is selected from naturalcalcium carbonate sources, preferably containing from 50 to 98 wt.-% ofcalcium carbonate, based on the total weight of said calciumcarbonate-comprising material.

According to one embodiment, the calcium carbonate-comprising materialcontains at least 50 wt.-%, preferably at least 70 wt.-%, morepreferably at least 80 wt.-%, even more preferably at least 90 wt.-%,and most preferably from 90 to 98 wt.-% of calcium carbonate, based onthe total weight of said calcium carbonate-comprising material.

According to another embodiment, the calcium carbonate-comprisingmaterial is selected from the group consisting of marble, limestone,chalk, dolomite, and mixtures thereof.

In cases where the calcium carbonate is of synthetic origin, the calciumcarbonate-comprising material may be precipitated calcium carbonate(PCC). A PCC in the meaning of the present invention is a synthesizedmaterial, generally obtained by precipitation following a reaction ofcarbon dioxide and calcium hydroxide (hydrated lime) in an aqueousenvironment or by precipitation of a calcium- and a carbonate source inwater. Additionally, precipitated calcium carbonate can also be theproduct of introducing calcium and carbonate salts, calcium chloride andsodium carbonate, for example, in an aqueous environment. PCC may bevaterite, calcite or aragonite. PCCs are described, for example, in EP 2447 213 A1, EP 2 524 898 A1, EP 2 371 766 A1, EP 2 840 065 A1, or WO2013/142473 A1.

According to one embodiment, the calcium carbonate-comprising materialhas a weight median particle size d₅₀ ranging from 5.0 to 600.0 μm andpreferably from 50.0 to 300.0 μm.

The layer comprising the coating composition (a) is preferably the undermost layer this means directly adjacent to the surface of the uncoatedpaper. It is essential that the ink layer (b) is arranged above layer(a), however it is possible that further layers, e.g. a layer comprisinga calcium carbonate-comprising material, are arranged between layers (a)and (b). But the ink layer (b) cannot be arranged between the surface ofthe uncoated paper and layer (a).

Preferred arrangements of layers on the coated paper are given below:

Paper-layer (a)-layer (b)

Paper-layer (a)-layer (c)-layer (b)

Paper-layer (a)-layer (c)-layer (c)-layer (b)

Paper-layer (a)-layer (c)-layer (a)-layer (b)

The arrangement “Paper-layer (a)-layer (c)-layer (a)-layer (b)” allowsto recycle the calcium carbonate-comprising material in layer (c).

Process Step (ii)

According to the present invention the activation of the calcium- ormagnesium-exchanged clay can be achieved by the following means:

(A) carrying out step (iii) with water comprising monovalent ionsselected from the group consisting of sodium, lithium, potassium,ammonium ions and mixtures thereof, and/or

(B) providing in step (i) a water-soluble binder (a2) comprisingmonovalent ions selected from the group consisting of sodium, lithium,potassium, ammonium ions and/or mixtures thereof, and/or

(C) adding monovalent ions selected from the group consisting of sodium,lithium, potassium, ammonium ions and mixtures thereof in form of asalt.

The activation is achieved by at least partially exchanging the calciumor magnesium ion with a monovalent cation, preferably with sodium, andtransforming the clay into its water-swellable form.

A similar concept may use a clay exchanged with a divalent cationdifferent from calcium or magnesium, or mixtures of divalent cationsincluding calcium and magnesium and exchange these cations with amonovalent cation like e.g. lithium or sodium.

According to one embodiment of the present invention step (iii) iscarried out with water having a sodium content in the range from 10 to10 000 mg/1, preferably 10 to 1 000 mg/l and more preferably 10 to 300mg/l.

In another embodiment of the present invention the water as provided instep (iii) has an excess of sodium ions with respect to calcium ions inthe range from 2:1 to 1 000 to 1.

According to a further embodiment the water applied in step (iii) is tapwater, and preferred is tap water comprising an excess of sodium ionswith respect to calcium or magnesium ions in the range from 2:1 to 1000:1.

In one embodiment the coating composition in layer (a) comprisesbentonite and carboxymethylcellulose, preferably acarboxymethylcellulose having an excess of sodium ions with respect tocalcium or magnesium ions. The sodium content of thecarboxymethylcellulose may be in the range from 1 to 40 wt.-% based onthe overall weight of the carboxymethylcellulose, preferably 5 to 15wt.-% based on the overall weight of the carboxymethylcellulose.

According to still another embodiment the coating composition comprisesa water-soluble binder, preferably a carboxymethylcellulose, having anexcess of sodium ions with respect to calcium ions in the range from10:1 to 100 000 to 1.

In case that monovalent ions selected from the group consisting ofsodium, lithium, potassium, ammonium ions and mixtures thereof are addedin form of a salt before or during step (iii) it is preferred that thesalt with respect to the amount of the calcium exchanged clay is addedin an excess of 50%, preferably 150% with respect to the mass of thesodium salt and the calcium exchanged clay. Preferred salts are sodiumsalts selected from the group consisting of sodium chloride, sodiumnitrate, sodium sulphate and sodium carbonate.

It is also possible to carry out step (ii) by applying a combination ofmeans (A) to (C), such as (A) and (B), (A) and (C), (B) and (C) or (A),(B) and (C).

The treatment with sodium hydroxide for activating the calcium-exchangedclay is not a preferred option, since a strong base, like sodiumhydroxide, can deactivate cationic collector agents, likepolyethyleneimines. The activity of these collector agents is essentialduring a further purification by flotation.

Without being bound by any theory it is believed that the presence ofmonovalent ions like sodium ions is sufficient for causing the deinkingof the paper or paperboard for some kinds of clay. An excess of thesemonovalent ions (especially sodium ions) with respect to calcium ormagnesium ions might be not mandatory but is preferred. There mightexist a rapid equilibrium between the calcium form (non-swollen) and thesodium form (swollen form) of the clay. Transforming the clay into theswollen form for a short time can be sufficient for effecting theexfoliation of the layer (a).

Process Step (iii)

According to step (iii) of the present invention the coated paper orpaperboard as provided in step (i) is treated with water to obtain anaqueous suspension comprising at least ink, clay particles and a paperpulp or paper residue.

The water effects an exchange of the cation in the calcium- ormagnesium-exchanged clay, whereupon swelling of the clay occurs andeffects detachment of layer (a) from the coated paper or paperboard.

In one embodiment mechanical scraping of the surface of the paper iscarried out during step (iii) to assist the detachment of layer (a) fromthe paper. Consequently, also layers (b) and if present other layersarranged on top of layer (a) are removed from the paper pulp or paperresidue. According to still another embodiment ultrasonication iscarried out during step (iii). In another embodiment mechanical scrapingand ultrasonication are carried out during step (iii) for supporting thedetachment of layer (a).

The treatment step (iii) can be carried out at a temperature in therange from 0 to 120° C., preferably from 10 to 100° C. and morepreferably from 15 to 40° C.

Optional Process Steps

The process according to the present invention may comprise furthersteps. According to one embodiment the processes comprises a step ofseparating the paper or paperboard from the aqueous suspension obtainedin step (iii). Mechanical separation steps like separation by using asieve or a centrifuge or sedimentation are preferred.

According to still another embodiment of the process according to thepresent invention the aqueous suspension obtained in step (iii) or (iv)is subjected to a flotation process for removal of the ink from thewater. The ink is transported out of the water together with the clay.

The process may comprise the following further steps for carrying outthe flotation:

-   -   (v) transferring the aqueous suspensions as obtained in        step (iii) or (iv) to a flotation cell, and/or    -   (vi) adding at least one collector agent to the aqueous        suspensions as obtained in step (iii), (iv) or (v), and    -   (vii) passing a flotation gas into the aqueous suspension formed        in step (vi) to obtain a phase comprising water and a froth        comprising nanoclay and ink, and    -   (viii) separating the froth as obtained in step (vii) from the        water.

The at least one collector agent used for imparting hydrophobicity tothe impurity fractions may be any means known to the skilled person.

The term “at least one” collector agent in the meaning of the presentinvention means that the collector agent comprises, preferably consistsof, one or more collector agents.

In one embodiment of the present invention, the at least one collectoragent comprises, preferably consists of, one collector agent.Alternatively, the at least one collector agent comprises, preferablyconsists of, two or more collector agents. For example, the at least onecollector agent comprises, preferably consists of, two or threecollector agents.

Preferably, the at least one collector agent comprises, more preferablyconsists of, one collector agent.

For example, the at least one collector agent is selected from the groupconsisting of modified polyethyleneimines, active and hydrophobictensides, preferably xanthate or thio phosphates, alkyl sulphates,polyalkylenimines, primary amines, tertiary amines, quaternary amines,fatty amines, esterquats, polyesterquats, and imidazolines or quaternaryimidazolium compounds, preferably quaternary imidazolium methosulphates,and most preferred are modified polyethyleneimines.

In one embodiment the modified polyethyleneimine is a hydrophobicallymodified polyethyleneimine, wherein the polyetyleneeimine ishydrophobically modified by replacement of all or part of the hydrogensof their primary and/or secondary amino groups by a functional group R,where R comprises a linear or branched or cyclic alkyl and/or aryl groupand contains 1 to 32 carbon atoms. Such modified polyethyleneimines are,e.g., described in EP 2 366 456 A1.

The solids content of the aqueous suspension as provided in step (iii)is preferably in the range from 0.1 to 75 wt. %, preferably from 0.5 to40 wt.-%, more preferably from 1 to 20 wt.-%.

The solids content of the aqueous suspension as provided in step (iv) ispreferably in the range from 0.01 to 75 wt. %, preferably from 0.5 to 40wt.-%, more preferably from 1 to 20 wt.-%.

Additionally or alternatively, the content of the at least one collectoragent is in the range from 0.001 to 50 wt.-% based on the total weightof the solids in the aqueous suspension as provided in step (iii) or(iv), preferably in the range from 0.002 to 20 wt.-% based on the totalweight of the solids in the aqueous suspension as provided in step (iii)or (iv), more preferably from 0.05 to 0.8 wt.-% based on the totalweight of the solids in the aqueous suspension as provided in step (iii)or (iv) and most preferably in the range from 0.02 to 0.1 wt.-%, basedon the total weight of the solids in the aqueous suspension as providedin step (iii) or (iv).

The flotation gas is preferably air.

It is preferred that the flotation gas feature a bubble size in thesuspension of between 0.01 and 10.0 mm.

The gas hold up is preferably between 5 to 35%.

During the flotation the aqueous suspension preferably has a temperatureof between 5 and 130° C., more preferably of between 10 and 100° C.,even more preferably of between 15 and 95° C. and most preferably ofbetween 20 and 95° C. The choice of the temperature highly depends onthe choice of the at least one collector agent.

It is appreciated that the process involves an indirect flotation stepleading to the formation of a froth containing ink and clay particlesand an aqueous suspension or solution bearing phase. If the coated papercomprises one or more further layers (c) comprising a calciumcarbonate-comprising material, it is preferred that the process involvesan indirect floatation step leading to the formation of a frothcontaining ink and clay particles and an aqueous suspension comprisingthe calcium carbonate-comprising material. The calciumcarbonate-comprising material may be further purified by e.g. a directflotation process leading to the formation of a froth containing thecalcium carbonate and an aqueous solution or by using a centrifuge.

In one embodiment, one or more additives selected from the groupconsisting of pH-adjusting agents, solvents, foaming agents such asisopropanol and polyelectrolytes are added before step (vii), preferablythe content of these additives is in the range from 0.0005 to 1.0 wt.-%,more preferably from 0.001 to 0.5 wt.-% and most preferably in the rangefrom 0.001 to 0.1 wt.-% based on the total weight of the solids in theaqueous suspension obtained after step (iii) or (iv).

EXPERIMENTAL SECTION

The scope and interest of the invention may be better understood onbasis of the following examples which are intended to illustrateembodiments of the present invention. However, they are not to beconstrued to limit the scope of the claims in any manner whatsoever.

1 Measurement Methods

In the following, measurement methods implemented in the examples aredescribed.

IR Spectroscopy

IR spectra of powders were measured on a Perkin-Elmer spectrometer witha universal ATR sampling accessory.

UV-VIS Spectroscopy

UV-VIS spectra of aqueous solutions/suspensions were recorded at roomtemperature on a Lambda 2 UV/Vis spectrometer (Perkin-Elmer, USA, scanspeed 240 nm/min) using a Perkin-Elmer UV-Vis cell (light path=10 mm).

Spectrophotometric Colour Evaluation

The spectrophotometric colour evaluation was carried out using a TechkonSP810 Lambda spectrophotometer (measurement mode: D2 CMYK, DinE,Illuminant: D65, observer: 10°)

Solids Content

The suspension solids content (also known as “dry weight”) wasdetermined using a Moisture Analyser MJ33 (Mettler-Toledo, Switzerland),with the following settings: drying temperature of 150° C., automaticswitch off if the mass does not change more than 1 mg over a period of30 s, standard drying of 1 to 10 g of suspension.

Ash Content

The ash content in wt.-% based on the total weight of the sample, wasdetermined by incineration of a sample in an incineration crucible whichwas put into an incineration furnace at 570° C. for 2 hours. The ashcontent was measured as the total amount of remaining inorganicresidues.

TGA

Thermogravimetric analysis (TGA) was performed using a Mettler ToledoTGA/DSC1 STARe system based on a sample of 5 to 500 mg and scanningtemperatures from 30 to 1 000° C. at a rate of 25° C./minute, under anair flow of 80 mL/min and a nitrogen gas flow of 20 ml/min for balanceprotection.

X-Ray Fluorescence Analysis (XRF)

For carrying out the XRF-measurement the samples were grinded to finepowder and then put into a plastic cassette on a 6 μm spectrolene film.The elemental composition of the sample was analysed under helium bysequential, wavelength dispersive X-ray fluorescence (using an ARL™PERFORM'X X-ray fluorescence spectrometer, Thermo Fisher Scientific,Inc., USA). The calculation of the elements was made by means ofsemi-quantitative calibration (UNIQUANT).

pH

pH was measured on a Mettler-Toledo Seven-Multi device. The pH of asuspension was measured at 24° C.±3° C. using a Mettler Toledo SevenEasy pH meter and a Mettler Toledo InLab® Expert Pro pH electrode(Mettler Toledo, Switzerland). A three point calibration (according tothe segment method) of the instrument was first made using commerciallyavailable buffer solutions having pH values of 4, 7 and 10 at 20° C.(from Aldrich). The reported pH values are the endpoint values detectedby the instrument (the endpoint is when the measured signal differs byless than 0.1 mV from the average over the last 6 s).

Ink Layer Thickness

The thickness of the ink layer was evaluated by light microscope. Themicrographs were taken under light microscope using transmitted lightand the brightfield method was applied to get a proper illumination ofthe sample. The thickness of the ink layer was measured at 4 differentspots on each image. The size of the pixel was 0.13 μm.

2 Paper Preparation

The tap water used in the following trials contained 15 ppm sodium ions.

2.1 Preparation of Coating Compositions

Coating Composition 1: Ca-Exchanged Bentonite Coating Composition

A Ca-exchanged bentonite coating colour was prepared from Na-Bentonite(Optigel CK, Rockwood additives) for use in the coating compositionaccording to Table 1.

TABLE 1 Coating composition 1 (=CC1), (Ca-exchanged bentonite coatingcomposition). parts dry w/w % based on Compound (tradename/supplier) 100parts by weight of clay Bentonite (Optigel CK, Rockwood 100 additives)Carboxy Methyl Cellulose 1.6 (Finnfix 10, CP, Kelco)

A 3 wt.-% solids content sodium form of bentonite was prepared. Thebentonite was first dispersed in tap water (38° C.), to aid the swellingof the tactoids. Additional sodium hydroxide was added to obtain a pH of11. The mixture was stirred for 15 minutes to produce an evenconsistency. In the resulting gel form the dispersed bentonite plateletsare surrounded by Na⁺ ions. The gel was allowed to age overnight (18 h)to avoid further post makedown thickening. To initiate the calcium ionexchange effect, calcium chloride was added. When adding Ca²⁺ ions tothe mixture, an intercalation between the bentonite platelets occurs.When adding calcium chloride step by step, the gel finally collapsed andit became fluid. This phenomenon occurred when the pH was between 8 and9. The fluid bentonite was filtered under vacuum using blue ribbon 589/3(<2 μm) filter paper to increase the solids content (8.5 to 12.0 wt.-%).The bentonite was rinsed with tap water during this process. Inpreparing the coating composition Carboxy Methyl Cellulose with 10 wt.-%dry solids content was added to re-thicken the mixture. The shade of theobtained coating colour was off-white-grey, and reflects the non-optimallight scattering cross-section of the bentonite in water. The finalsolids content was 7.1 wt.-%.

Coating Composition 2: GCC Colour for Top Coating

TABLE 2 Coating composition 2 (=CC2). Amount (solids content/parts perhundred based on 100 parts Compound (tradename/supplier) by weight ofpigment) GCC (Hydrocarb 95, Omya) 77.9 wt.-%/100 Polyvinyl alcohol 25wt.-%/0.2 Binder (Styronal D628/BASF) 60 wt.-%/9 Thickening agent 24wt.-%/0.4 (Rheocarb 131/Arkema) Optical brightening agent 100 wt.-%/0.5(OBA-APA/Tetra Sulpho) Water has been added to adjust the solids contentto 47.8 wt.-%.

To obtain coating composition 2, polyvinylalcohol, Styronal D628,Rheocarb 131 and OBA-APA/Tetra Sulpho were successively added to a GCCslurry, and homogenized at room temperature with a Pendraulik LD50 highspeed disperser (50 mm diam. dispersing disc, speed approx. 1 250 rpm)for 2 to 5 minutes after each component had been added.

2.2 Preparation of Coated Papers

Paper 1 is a commercially available A4 copy-grade paper (Cento Plus, 80g/m², uncoated)

Paper 2 is a SAPPI pre-coated with ground calcium carbonate A4 paper(100% GCC pre-coating)

Paper 3 is an uncoated copy-grade paper (80 g/m2, paper 1) coated withcoating composition 1 on a C-Coater (coater speed 3, rod type 5),coating weight FS: 3.6 g/m²

Paper 4 is a SAPPI GCC pre-coated paper (paper 2) coated withcomposition 1 on a C-Coater (coater speed 3, rod type 5), and then cutto A4 format, coating weight FS: 3.9 g/m²

Paper 5 is paper 3, which was further coated with coating composition 2on a C-Coater (coater speed 3, rod type 3), and then cut to A4 format,coating weight FS: 8.5 g/m²

2.3 Paper Printing

-   -   Two inkjet printing systems were used: Canon Pixma iP4850        (Chromalife 100 dye-based ink; print head system Bubble Jet,        thermal InkJet; print head: Fine Print Head 1 pl, 512 nozzle        k,Y,PBK+1536 nozzle c,m; print settings: standard, high        resolution paper; Print resolution: 9 600×2 400 dpiHP OfficeJet        Pro 8000 Enterprise (Pigment-based ink; print head system Bubble        Jet, thermal InkJet; print head: 2 Printhead à 2112 nozzle;        print settings: normal, optimal; Print resolution: 4 800×1 200        dpi)

In addition, offset printing was done on an ISIT system (printing of210×21 mm² bands) with a Skinnex cyan ink.

Format 1 is 185×288 mm² rectangle printout in cyan colour on an A4 papersheet for a total printed area of 532.8 cm².

Format 2 is an arrangement of 6 cyan rectangle printouts (24×95 mm²), 6Magenta rectangle printouts (24×95 mm²), and 5 black rectangle printouts(24×190 mm²) on a A4 paper sheet for a total printed area of 501.6 cm².

Format 3 is composed of 7 printed strips (ca. 210×21 mm², printed withSkinnex cyan ink).

TABLE 3 Overview printed papers. No. Sample Paper Coating CoatingCoating Printing of ink ref used layer 1 layer 2 layer 3 Ink type formatlayers Printed Paper CC2 — — Pigment Format 1 paper 6 2 2 Printed PaperCC2 — — Dye Format 1 paper 7 2 2 Printed Paper CC2 — — Pigment Format 3paper 8 2 2 Printed Paper CC2 — — Offset Format 3 paper 9 2 3 PrintedPaper CC2 CC1 — Pigment Format 1 paper 10 4 1 Printed Paper CC2 CC1 —Pigment Format 1 paper 11 4 2 Printed Paper CC2 CC1 — Offset Format 1paper 12 4 3 Printed Paper CC2 CC1 — Pigment Format 3 paper 13 4 1Printed Paper CC2 CC1 — Pigment Format 3 paper 14 4 2 Printed Paper CC2CC1 — Offset Format 3 paper 15 4 3 Printed Paper CC2 CC1 CC2 PigmentFormat 1 paper 16 5 2 Printed Paper CC2 CC1 CC2 Dye Format 1 paper 17 52

Printing of Paper 9

The paper used was an 80 g/m² SAPPI pre-coated (GCC) paper, which wasprinted on the ISIT (Ink surface interaction tester) with an offset ink(3 times). 1 sheet of paper 2 was cut in 7 paper bands, and printed onthe ISIT with cyan offset ink (3 times, 1 h drying time between twosuccessive layers).

Printing of Paper 13

The paper was printed with inkjet pigment ink on format 1 and then leftto dry for 10 minutes. Afterwards the printing was performed again ontop of the 1^(st) layer, and, after 10 minutes drying, a 3^(rd) inklayer was printed.

Printing of Paper 14

The paper was printed with inkjet pigment ink on format 2, then left todry for 10 minutes. The printing was then performed again on top of the1^(st) layer, and, after 10 minutes drying, a 3^(rd) ink layer wasprinted.

Printing of Paper 15

The paper used was a SAPPI pre-coated (GCC) paper, which was coated witha bentonite layer and printed on the ISIT (Ink surface interactiontester) with an offset ink (3 times).

1 A4 sheet of paper was cut vertically in 7 pieces, and printed on theISIT with cyan offset ink (Novavit 4×800 SKINNEX Cyan, 3 consecutiveprinted layers on top of each other, 1 h drying time between twosuccessive layers).

3 Deinking and Floatation with Pigmented Ink

The tap water used in the following trials contained 15 ppm sodium ions.The modified polyethyleneimine polymer that has been used in thefollowing trials has a polyethyleneimine backbone with a molecularweight (M_(w)) of 5 000 g/mol and is modified with a saturated C5 fattyacid as described in EP 2 366 456 A1.

Example 1: Deinking and Flotation of Printed Paper 11 (InventiveExample)

Step A): Ink Desorption from Paper

One A4 printed paper 11 sheet was dipped in a beaker (5 L) in 2.2 Ldeionized water and was left to stay without particular stirring during10 minutes. The ink “slipped” from the sheet in large particles and theblack colour was completely removed, whereas blue and red schemes leaveslightly red/pink colour traces on the paper. Afterwards, thedecolourized paper was removed from the beaker and the water with inkparticles in suspension were directly used for flotation purification.The pH of the obtained mixture was 9.1.

Step B): Purification by Flotation

Flotation was performed on an Outotec Labcell flotation device. 2 L ofthe aqueous suspension obtained in step A) were placed in the flotationflask. The mixture was stirred for 2 minutes under air flow (55 Hz, 1650 rpm, air flow: 4 to 6 l/min). After that period of time, a modifiedpolyethyleneimine polymer (1.0 g, 7.5 wt.-% solid content) was added.The air flow was stopped and the mixture was stirred for additional 2minutes. The air flow was then turned on for 20 minutes (4 to 6 l/min).A pink/purple coloured foam appeared, and the water suspension becameclearer after 2 minutes. After that period of time, the water sample wasvisually free from coloured particles. The flotation was stopped, andthe different fractions (removed foam and clean water) were analysed.

Waste (removed foam fraction): dark purple, V=250 ml, pH=8.3 Cleanwater: colourless with trace amount of particles in suspension, V=1.75l, pH=8.3.

Step C: Filtration

The waste fraction was filtered by using a Buchner funnel (Whatman grade589/3 qualitative filtration paper), washed with deionized water anddried under reduced pressure at 90° C. for 4 h. 80 mg of a dark powderwere recovered and analysed.

Analyses

IR

The waste fraction showed a Peak at 1 000 cm⁻¹ that can be attributed tothe bentonite (Si—O bond, see FIG. 1).

UV/Vis

FIG. 2 shows the UV-vis spectra of the aqueous suspension before andafter the flotation (once filtered).

Spectrophotometry

Cyan density was measured on the blue-printed portions

Magenta density was measured on the red-printed portions

Black density was measured on the black-printed portions

Given values are an average of 10 measurements.

TABLE 4 Results of spectrophotometric evaluation. Sample Cyan MagentaBlack Example 1/Printed paper 11 before step A 1.3321 1.299 1.5475Example 1/Printed paper 11 after step A 0.0264 0.1018 0.0231

Composition Analysis

The compositions of the different fractions of materials were analysedusing the following techniques:

-   -   Determination of the ash content    -   Thermogravimetric analysis    -   Semiquantitative XRF-analysis (UNIQUANT)    -   FTIR-spectra

The results are summarized in Tables 5 and 6 below.

TABLE 5 Composition of different fractions. Ash content Fraction [wt.-%]Composition/Remarks Printed paper 11 31.0 Mainly paper (cellulose), ashbefore step A contains mainly CaCO₃ (25 wt.-%), Al-silicates (5 wt.-%)Printed paper 11 30.4 Mainly paper (cellulose), ash after step Acontains mainly CaCO₃ (26 wt.-%), some Al-silicates (4 wt.-%) Wastecollected 57 Mainly inorganics, especially after step B flotationAl-Silicates (45 wt.-%), CaCO₃ (10 wt.-%)

TABLE 6 Composition of different fractions. Printed Printed Wastecollected paper 11 paper 11 after step B before step A after step Aflotation CaO  13.9 wt.-%  13.7 wt.-% 2.95 wt.-% MgO  0.95 wt.-%  0.91wt.-% 2.75 wt.-% Al₂O₃  1.38 wt.-%  1.13 wt.-% 9.45 wt.-% SiO₂  3.38wt.-%  2.42 wt.-% 32.6 wt.-% Fe₂O₃  0.25 wt.-%  0.11 wt.-% 1.57 wt.-%TiO₂  0.04 wt.-%  0.02 wt.-% 0.14 wt.-% SO₃  0.06 wt.-%  0.04 wt.-% 0.18wt.-% Na₂O  0.20 wt.-% — 0.21 wt.-% Others  0.08 wt.-%  0.10 wt.-% 0.05wt.-% TGA 30-250° C.  0.17 wt.-%  0.14 wt.-% 7.0 wt.-% (→water) TGA250-1000° C. 10.54 wt.-% 11.74 wt.-% (→CO₂) Organic content  69.0 wt.-% 69.6 wt.-% 43 wt.-%

Example 2: Deinking and Flotation of Printed Paper 16 (InventiveExample)

Step A): Ink Desorption from Paper

One A4 printed paper 16 sheet was dipped in a beaker (5 l) in 2.2 ldeionised water and was left to stay without particular stirring during10 minutes. The ink “slipped” from the sheet in very large platelets andthe black colour was completely removed, whereas blue and red schemesleave slightly red/pink colour traces on the paper. Afterwards, thedecolourized paper was removed from the beaker and the water with inkparticles in suspension (slightly red in colour and trouble aspects)were directly used for flotation purification. The pH of the obtainedmixture was 9.1.

Step B): Purification by Flotation

Flotation was performed on an Outotec Labcell flotation device. 21 ofthe aqueous suspension obtained in step A) were placed in the flotationflask. The mixture was stirred for 2 minutes under air flow (55 Hz, 1650 rpm, air flow: 4 to 6 l/min). After that period of time, a modifiedpolyethyleneimine polymer (1.0 g, 7.5 wt.-% solid content) was added.The air flow was stopped and the mixture was stirred for additional 2minutes. The air flow was then turned on for 20 minutes (4 to 6 l/min).A pink/purple coloured foam comprising pink/purple ink particlesappeared. Rapid decolourization of the water sample was observed, butlots of ink particles remain in suspension. Another 0.5 g of themodified polyethyleneimine polymer were added, which lead to formationof a colourless foam with ink particles on the surface. After 20minutes, no more ink particle were observed at the surface. Theflotation was stopped, and the different fractions (removed foam andclean water) were analysed. Waste (removed foam fraction): dark purple,V=200 ml, pH=8.5

Clean water: colourless with traces of small ink particles remaining insuspension, V=1.81, pH=8.3.

Step C: Filtration

The waste fraction was filtered by using a Buchner funnel (Whatman grade589/3 qualitative filtration paper), washed with deionized water anddried under reduced pressure at 90° C. for 4 h. 0.9 g ofpurple/multicolour particles were recovered and analysed.

Analyses

IR

The waste fraction showed a Peak at 1 000 cm⁻¹ that can be attributed tothe bentonite (Si—O bond, see FIG. 3) and a peak at 1 400 cm⁻¹ that canbe attributed to calcium carbonate.

UV/Vis

FIG. 4 shows the UV-vis spectra of the aqueous suspension before andafter the flotation (once filtered).

Spectrophotometry

Cyan density was measured on the blue-printed portions

Magenta density was measured on the red-printed portions

Black density was measured on the black-printed portions

Given values are an average of 10 measurements.

TABLE 7 Results of spectrophotometric evaluation. Sample Cyan MagentaBlack Example 2/Printed paper 16 before step A 1.6269 1.569 1.6735Example 2/Printed paper 16 after step A 0.0292 0.0917 0.0468

Composition Analysis:

TABLE 8 Composition of different fractions. Ash content Fraction [wt.-%]Composition/Remarks Printed paper 16 36.8 Mainly paper (cellulose), 30wt.-% before step A CaCO₃, 6 wt.-% Al-Silicates, coating binder Printedpaper 16 29.7 Mainly paper (cellulose), about after step A 26 wt.-%CaCO₃, 4% Al-Silicates, coating binder Waste collected 85.2 Mainlyinorganic, most of it (>60%) after step B flotation CaCO₃, 20 wt.-%Al-Silicate

TABLE 9 Composition of different fractions. Printed Printed Wastecollected paper 16 paper 16 after step B before step A after step Aflotation CaO  18.7 wt.-%  14.5 wt.-% 34.0 wt.-% MgO  0.98 wt.-%  0.92wt.-% 1.48 wt.-% Al₂O₃  0.96 wt.-%  0.88 wt.-% 3.33 wt.-% SiO₂  2.31wt.-%  1.65 wt.-% 10.6 wt.-% Fe₂O₃  0.22 wt.-%  0.10 wt.-% 0.47 wt.-%TiO₂  0.03 wt.-%  0.02 wt.-% 0.05 wt.-% SO₃  0.07 wt.-%  0.05 wt.-% 0.07wt.-% Na₂O — — — Others  0.15 wt.-%  0.08 wt.-% 0.22 wt.-% TGA 30-250°C.  0.16 wt.-%  0.19 wt.-% 35.0 wt.-% (→water) TGA 250- 1000° C. 13.20wt.-% 11.31 wt.-% (→CO₂) Organic content  63.2 wt.-%  70.3 wt.-% 14.7wt.-%

Example 3: Deinking and Flotation of Printed Paper 6 (ComparativeExample)

Step A): Ink Desorption from Paper

One A4 printed paper 16 sheet was dipped in a beaker (5 l) 2.2 l tapwater and was left to stay without particular stirring during 10minutes. No visible particles were released in the tap water, and nodecolourization of the paper was observed. Only a slight pinkcolourization of water was observed.

Spectrophotometry

Cyan density was measured on the blue-printed portions

Magenta density was measured on the red-printed portions

Black density was measured on the black-printed portions

Given values are an average of 10 measurements.

TABLE 10 Results of spectrophotometric evaluation. Sample Cyan MagentaBlack Example 3/Printed paper 6 before step A 1.345 1.2581 1.5618Example 3/Printed paper 6 after step A 1.2585 1.151 1.5339

Example 4: Deinking and Flotation of Printed Paper 13 (InventiveExample)

Step A): Ink Desorption from Paper

One A4 printed paper 13 sheet was dipped in a beaker (5 l) in 2.2 l tapwater. The mixture was regularly agitated during 10 minutes. The ink“slipped” slowly from the sheet in small platelets and the black colourwas completely removed, whereas blue and red schemes leave slightlyred/pink colour traces on the paper. Afterwards, the decolourized paperwas removed from the beaker and the water with ink particles insuspension (slightly purple in colour and trouble aspect) were directlyused for flotation purification. The pH of the obtained mixture was 7.9.

Step B): Purification by Flotation

Flotation was performed on an Outotec Labcell flotation device. 21 ofthe aqueous suspension obtained in step A) were placed in the flotationflask. The mixture was stirred for 2 minutes under air flow (55 Hz, 1650 rpm, air flow: 4 to 6 l/min). After that period of time, a modifiedpolyethyleneimine polymer (0.8 g, 11.0 wt.-% solid content) was added.The air flow was stopped and the mixture was stirred for additional 2minutes. The air flow was then turned on for 20 minutes (4 to 6 l/min).A pink/purple coloured foam comprising pink/purple with large inkparticles appeared. Rapid decolourization of the water sample wasobserved, but visible ink particles remain in suspension. Another 0.4 gof the modified polyethyleneimine polymer were added, which lead toformation of a colourless foam with ink particles on the surface. After10 minutes complete decolourization occurred. The flotation was stopped,and the different fractions (removed foam and clean water) wereanalysed.

Waste (removed foam fraction): dark purple, V=300 ml, pH=8.2

Clean water: colourless, no significant amount of particles present,V=1.7 l, pH=8.0.

Step C: Filtration

The waste fraction was filtered by using a Buchner funnel (Whatman grade589/3 qualitative filtration paper), washed with deionized water anddried under reduced pressure at 90° C. for 4 h. 0.28 g of purple/colourparticles were recovered and analysed.

Analyses

IR

The waste fraction showed a Peak around 1 000 cm⁻¹ that can beattributed to the bentonite (Si—O bond, see FIG. 5) and a peak around 1400 cm-1 that can be attributed to calcium carbonate.

UV/Vis

FIG. 6 shows the UV-vis spectra of the aqueous suspension before andafter the flotation.

Spectrophotometry

Cyan density was measured on the blue-printed portions

TABLE 11 Results of spectrophotometric evaluation. Sample Cyan Example4/Printed paper 13 before step A 1.5672 Example 4/Printed paper 13 afterstep A 0.0673

Ink Layer Thickness:

TABLE 12 Ink layer thickness before and after exposure to water. AverageStandard deviation Sample thickness (μm) (μm) Printed paper 13 before3.5 1.1 exposure to water Printed paper 13 after no ink visible —exposure to water Printed paper 10 before 1.9 0.7 exposure to waterPrinted paper 10 after no ink visible — exposure to water

Composition Analysis:

TABLE 13 Composition of different fractions. Ash content Fraction[wt.-%] Composition/Remarks Printed paper 13 30.2 Mainly paper(cellulose), 25 wt.-% before step A CaCO₃, 5 wt.-% Al-Silicates Printedpaper 13 44.9 Mainly inorganics, especially after step A Al-silicates(30 wt.-%) and CaCO₃ (15 wt.-%)

TABLE 14 Composition of different fractions. Printed paper 13 Printedpaper 13 before step A after step A CaO 13.26 wt.-%  7.04 wt.-% MgO 1.00 wt.-%  1.88 wt.-% Al₂O₃  1.20 wt.-%  6.00 wt.-% SiO₂  2.60 wt.-%20.12 wt.-% Fe₂O₃  0.09 wt.-%  0.82 wt.-% TiO₂  0.02 wt.-%  0.08 wt.-%SO₃  0.04 wt.-%  0.14 wt.-% Na₂O  0.06 wt.-%  0.40 wt.-% Others  0.07wt.-%  0.17 wt.-% TGA 30-250° C.  0.24 wt.-%  1.59 wt.-% (→water) TGA250-1000° C. 11.63 wt.-%  6.66 wt.-% (→CO₂) Organic content  69.8 wt.-% 55.1 wt.-%

Example 5: Deinking and Flotation of Printed Paper 14 (InventiveExample)

Step A): Ink Desorption from Paper

One A4 printed paper 14 sheet was dipped in a beaker (5 l) in 2.2 l tapwater. The mixture was regularly agitated during 10 minutes. The ink“slipped” slowly from the sheet in small particles, pink colour tracesremained on the paper from blue and especially from red printed areas.Afterwards, the decolourized paper was removed from the beaker and thewater with ink particles in suspension was directly used for flotationpurification. The pH of the obtained mixture was 7.4.

Step B): Purification by Flotation

Flotation was performed on an Outotec Labcell flotation device. 2 L ofthe aqueous suspension obtained in step A) were placed in the flotationflask. The mixture was stirred for 2 minutes under air flow (55 Hz, 1650 rpm, air flow: 4 to 6 l/min). After that period of time, a modifiedpolyethyleneimine polymer (0.8 g, 11.0 wt.-% solid content) was added.The air flow was stopped and the mixture was stirred for additional 2minutes. The air flow was then turned on for 20 minutes (4 to 6 l/min).A pink/purple coloured foam comprising pink/purple with large inkparticles appeared. Rapid decolourization of the water sample wasobserved, but visible ink particles remain in suspension. After 10minutes another 0.6 g of the modified polyethyleneimine polymer wereadded, which lead to formation of a colourless foam with ink particleson the surface. After 10 minutes complete decolourization occurred,although some tiny dark particles (black) of ink remain in suspension.The flotation was stopped, and the different fractions (removed foam andclean water) were analysed.

Waste (removed foam fraction): dark purple, V=300 ml, pH=8.2

Clean water: colourless, no significant amount of particles present,V=1.7 l, pH=8.0.

Step C: Filtration

The waste fraction was filtered by using a Buchner funnel (Whatman grade589/3 qualitative filtration paper), washed with deionized water anddried under reduced pressure at 90° C. for 4 h. 0.26 g of purple/colourparticles were recovered and analysed.

Analyses

IR

The waste fraction showed a Peak at 1 000 cm⁻¹ that can be attributed tothe bentonite (Si—O bond), (FIG. 7).

Spectrophotometry

Cyan density was measured on the blue-printed portions

Magenta density was measured on the red-printed portions

Black density was measured on the black-printed portions

Given values are an average of 10 measurements.

TABLE 15 Results of spectrophotometric evaluation. Sample Cyan MagentaBlack Example 5/Printed paper 1.55 1.52 (1.64 on blue sections) 1.66 14before step A Example 5/Printed paper 0.084 0.267 (0.206 on bluesections) 0.061 14 after step A

Composition Analysis

TABLE 16 Composition of different fractions. Ash content Fraction[wt.-%] Composition/Remarks Waste collected after 46.6 Mainly organics(Cellulose), step B flotation 31 wt.-% CaCO₃, 12 wt.-% Al-silicate

TABLE 17 Composition of different fractions. Waste collected after stepB flotation CaO  4.34 wt.-% MgO  2.13 wt.-% Al₂O₃  7.02 wt.-% SiO₂ 23.75wt.-% Fe₂O₃  0.89 wt.-% TiO₂  0.08 wt.-% SO₃  0.16 wt.-% Na₂O  0.33wt.-% Others  0.27 wt.-% TGA 30-250° C.  2.42 wt.-% (→water) TGA250-1000° C.  5.17 wt.-% (→CO₂) Organic content  53.4 wt.-%

Example 6: Deinking and Flotation of Printed Paper 6 (ComparativeExample)

Step A): Ink Desorption from Paper:

One A4 printed paper 6 sheet is dipped in 21 deionized water and left tostay without particular stirring during 10 minutes. No visible particlesare released in water, and the paper does not decolourize. Only a slightpink colourization of water can be observed.

Spectrophotometry for Colour Evaluation:

Cyan density was measured on the blue-printed portions

Magenta density was measured on the red-printed portions

Black density was measured on the black-printed portions

TABLE 18 Results of spectrophotometric evaluation. Sample Cyan MagentaBlack Example 6/Printed paper 6 before step A 1.345 1.2581 1.5618Example 6/Printed paper 6 after step A 1.2585 1.151 1.5339

Example 7: Deinking and Flotation of Printed Paper 8 (ComparativeExample)

Step A): Ink Desorption from Paper

One A4 printed paper 8 sheet was dipped in a beaker (5 l) in 2 l tapwater and manually agitated regularly for 10 minutes. Almost no visibleparticles are released in water and the paper does not decolourize. Onlya slight pink colourization of the tap water was observed. Afterwards,the paper sheet was removed from the beaker and the colour densitymeasured on each section.

Spectrophotometry for Colour Evaluation

Cyan density was measured on the blue-printed portions

Magenta density was measured on the red-printed portions

Black density was measured on the black-printed portions

Given values are an average of 10 measurements.

TABLE 19 Results of spectrophotometric evaluation. Sample Cyan MagentaBlack Example 7/Printed paper 8 before step A 1.59 1.57 1.64 Example7/Printed paper 8 after step A 1.41 1.36 1.43

Example 8: Deinking and Flotation of Printed Paper 17 (InventiveExample)

Step A): Ink Desorption from Paper

One A4 printed paper 17 sheet was dipped in a beaker (5 l) in 2.2 ldeionized water and was left to stay without particular stirring for 1h. Some ink dissolved (blue colouration) and particles “slipped” fromthe sheet. After another 1 hour, the decolourized paper was removed fromthe beaker and colour traces can still be seen on the paper surface. Thewater (deep blue in colour) with ink particles in suspension (theparticles sedimented rapidly) was directly used for flotationpurification. The pH of the obtained mixture was 8.1.

Step B): Purification by Flotation

Flotation was performed on an Outotec Labcell flotation device. 21 ofthe aqueous suspension obtained in step A) were placed in the flotationflask. The mixture was stirred for 2 minutes under air flow (55 Hz, 1650 rpm, air flow: 4 to 6 l/min). After that period of time, a modifiedpolyethyleneimine polymer (1.0 g, 7.5 wt.-% solid content) was added.The air flow was stopped and the mixture was stirred for additional 2minutes. The air flow was then turned on for 10 minutes (4 to 6 l/min).A dark particles containing foam appeared, after 10 minutes reducedfoaming was observed, although the sample remained quite coloured.Another 1 g (7.5 wt.-% solid content) of the modified polyethyleneiminepolymer were added and the flotation was continued for another 10minutes. Complete decolourization of the sample occurred, the sample wasvisually free from coloured particles but some trace amount of whiteparticles remained in the suspension. The flotation was stopped, and thedifferent fractions (removed foam and clean water) were analysed.

Waste (removed foam fraction): dark purple, V=300 ml, pH=8.3

Clean water: colourless, no significant amount of particles present,V=1.7 l, pH=7.6

Step C: Filtration

The waste fraction was filtered by using a Buchner funnel (Whatman grade589/3 qualitative filtration paper), washed with deionized water anddried under reduced pressure at 90° C. for 4 h. 0.39 g of a grey powderwere recovered and analysed.

Analyses

IR

The waste fraction showed a Peak at 1 000 cm⁻¹ that can be attributed tothe bentonite (Si—O bond, see FIG. 8) and a peak at 1 400 cm⁻¹ that canbe attributed to calcium carbonate.

UV/Vis

FIG. 9 shows the UV-vis spectra of the aqueous suspension before andafter the flotation.

Spectrophotometry

Cyan density was measured on the blue-printed portions

Magenta density was measured on the red-printed portions

Black density was measured on the black-printed portions

Given values are an average of 10 measurements.

TABLE 20 Results of spectrophotometric evaluation. Sample Cyan MagentaBlack Example 8/Printed paper 17 before step A 1.2388 0.9301 1.0467Example 8/Printed paper 17 after step A 0.163 0.2073 0.2387

Composition Analysis

TABLE 21 Composition of different fractions. Ash content Fraction[wt.-%] Composition/Remarks Printed paper 17 30.1 Mainly coated paper(cellulose) & before step A coating binders, 27 wt.-% CaCO₃, 3 wt.-%Al-Silicates Flotation waste 67.5 43 wt.-% CaCO₃ and 26 wt.-% after stepB Al-Silicates, organic polymers

TABLE 22 Composition of different fractions. Printed paper 17 Flotationwaste after before step A step B CaO  14.1 wt.-%  22.8 wt.-% MgO  0.95wt.-%  1.54 wt.-% Al₂O₃  0.93 wt.-%  4.28 wt.-% SiO₂  1.78 wt.-%  15.3wt.-% Fe₂O₃  0.09 wt.-%  0.81 wt.-% TiO₂  0.02 wt.-%  0.08 wt.-% SO₃ 0.04 wt.-%  0.93 wt.-% Na₂O — — Others  0.11 wt.-%  0.42 wt.-% TGA30-250° C.  0.15 wt.-%  1.28 wt.-% (→water) TGA 250-1000° C. 11.93 wt.-%20.07 wt.-% (→CO₂) Organic content  69.9 wt.-%  32.5 wt.-%

Example 9: Deinking and Flotation of Printed Paper 7 (ComparativeExample)

Step A): Ink Desorption from Paper

One A4 printed paper 7 sheet was dipped in a beaker (5 l) in 2.2 ldeionized water and was left to stay without particular stirring for 1h. Some ink dissolved and particles got into the water (dissolution andsuspension). After another 1 hour, the decolourized paper was removedfrom the beaker and colour traces can still be seen on the papersurface. The water (deep blue in colour) with ink particles insuspension (the particles sedimented rapidly) was directly used forflotation purification. The pH of the obtained mixture was 7.9.

Step B): Purification by Flotation

Flotation was performed on an Outotec Labcell flotation device. 2 L ofthe aqueous suspension obtained in step A) were placed in the flotationflask. The mixture was stirred for 2 minutes under air flow (55 Hz, 1650 rpm, air flow: 4 to 6 l/min). After that period of time, a modifiedpolyethyleneimine polymer (1.0 g, 7.5 wt.-% solid content) was added.The air flow was stopped and the mixture was stirred for additional 2minutes. The air flow was then turned on for 10 minutes (4 to 6 l/min).A dark particles containing foam appeared, after 10 minutes reducedfoaming was observed, although the sample remained quite coloured.Another 1 g (7.5 wt.-% solid content) of the modified polyethyleneiminepolymer were added and the flotation was continued for another 10minutes. After that time the water sample was almost colourless (slightblue colour). The flotation was stopped, and the different fractions(removed foam and clean water) were analysed.

Waste (removed foam fraction): dark purple, V=200 ml, pH=7.3

Clean water: colourless, no significant amount of particles present,V=1.8 l, pH=7.2.

Analyses

Spectrophotometry

Cyan density was measured on the blue-printed portions

Magenta density was measured on the red-printed portions

Black density was measured on the black-printed portions

Given values are an average of 10 measurements.

TABLE 23 Results of spectrophotometric evaluation. Sample Cyan MagentaBlack Example 9/Printed paper 7 before step A 1.0821 0.7461 1.028Example 9/Printed paper 7 after step A 0.2254 0.2739 0.3384

Composition Analysis

TABLE 24 Composition of different fractions. Ash content Fraction[wt.-%] Composition/Remarks Printed paper 7 after 28.7 Mainly coatedpaper (cellulose) and step A coating binders, 27 wt.-% CaCO₃, 2.5 wt.-%Al-Silicates

TABLE 25 Composition of different fractions. Printed paper 7 after stepA CaO  15.0 wt.-% MgO  0.95 wt.-% Al₂O₃  0.75 wt.-% SiO₂  1.22 wt.-%Fe₂O₃  0.07 wt.-% TiO₂  0.02 wt.-% SO₃  0.06 wt.-% Na₂O — Others  0.13wt.-% TGA 30-250° C.  0.10 wt.-% (→water) TGA 250-1000° C. 12.71 wt.-%(→CO₂) Organic content  69.0 wt.-%

Example 10: Deinking and Flotation of Paper 15 (Inventive Example)

Step A): Ink Desorption from Paper

One A4 printed paper 15 sheet was dipped in a beaker (5 l) in 2.2 l tapwater and was left to stay without particular stirring for 1 h. Thepaper was relatively hydrophobic and ink went off after paper was reallywet and manual agitation was required to remove the ink layer. After 10minutes the decolourized paper was removed from the beaker and thecoloured water with dispersed ink particles was directly used forflotation purification. The pH of the obtained mixture was 7.4.

Step B): Purification by Flotation

Flotation was performed on an Outotec Labcell flotation device. 21 ofthe aqueous suspension obtained in step A) were placed in the flotationflask. The mixture was stirred for 2 minutes under air flow (55 Hz, 1650 rpm, air flow: 4 to 6 l/min). After that period of time, a modifiedpolyethyleneimine polymer (0.8 g, 11 wt.-% solid content) was added. Theair flow was stopped and the mixture was stirred for additional 2minutes. The air flow was then turned on for 10 minutes (4 to 6 l/min).An almost colourless foam appeared containing the blue ink particles.Another 0.6 g (7.5 wt.-% solid content) of the modifiedpolyethyleneimine polymer were added and the flotation was continued foranother 10 minutes. After that time the water sample was almostcolourless and free from particles. The flotation was stopped after atotal time of 20 minutes, and the different fractions (removed foam andclean water) were analysed.

Waste (removed foam fraction): blue-coloured water and particles, V=300ml, pH=8.1

Clean water: colourless, no significant amount of particles present,V=1.7 l, pH=8.1.

Step C: Filtration

The waste fraction was filtered by using a Buchner funnel (Whatman grade589/3 qualitative filtration paper), washed with deionized water anddried under reduced pressure at 90° C. for 4 h. 0.25 g of blue and whiteparticles were recovered and analysed. The “clean” fraction from theflotation was also filtered and no residue was collected on filter.

IR

The waste fraction showed a Peak at 1 000 cm⁻¹ that can be attributed tothe bentonite (FIG. 10).

Spectrophotometry

Cyan density was measured on the blue-printed portions

Given values are an average of 10 measurements.

TABLE 26 Results of spectrophotometric evaluation. Sample Cyan Example10/Printed paper 15 before step A 1.9468 Example 10/Printed paper 15after step A 0.0462

Composition Analyses

TABLE 27 Composition of different fractions. Ash content Fraction[wt.-%] Composition/Remarks Printed paper 15 28.4 Mainly paper(cellulose), ash contains after step A 25 wt.-% CaCO₃ and 4 wt.-% clayPrinted paper 15 45.2 Enrichment of inorganics, contains before step A10 wt.-% CaCO₃ and 35 wt.-% Al-Silicates

TABLE 28 Composition of different fractions. Printed paper Wastecollected after 15 after step A step B CaO 13.55 wt.-%  6.06 wt.-% MgO 1.00 wt.-%  1.85 wt.-% Al₂O₃  0.86 wt.-%  6.06 wt.-% SiO₂  1.59 wt.-%22.77 wt.-% Fe₂O₃  0.08 wt.-%  0.84 wt.-% TiO₂  0.02 wt.-%  0.08 wt.-%SO₃  0.04 wt.-%  0.09 wt.-% Na₂O  0.04 wt.-%  0.09 wt.-% Others  0.07wt.-%  0.30 wt.-% TGA 30-250° C.  0.22 wt.-%  1.66 wt.-% (→water) TGA250-1000° C. 10.90 wt.-%  5.34 wt.-% (→CO₂) Organic content  71.6 wt.-% 54.8 wt.-%

Ink Layer Thickness:

TABLE 29 Ink layer thickness before and after exposure to water. AverageStandard deviation Sample thickness (μm) (μm) Printed paper 15 before3.8 2.4 exposure to water Printed paper 15 after no ink visible —exposure to water Printed paper 12 before 2.6 0.7 exposure to waterPrinted paper 12 after no ink visible — exposure to water

was measured at 4 different spots on each image. The size of the pixelwas 0.13 μm.

Example 11: Deinking and Flotation of Paper 9, (Comparative Example)

Step A): Ink Desorption from Paper

6.5 paper bands from paper 9 (dimension 21×215 mm²) were dipped in abeaker (5 l) in 2.2 l tap water and was left to stay without particularstirring for 1 h. The paper was relatively hydrophobic and ink went offafter paper was really wet and manual agitation for 10 minutes wasrequired to remove the ink layer. Nothing came off the paper, after 10minutes the decolourized paper was removed from the beaker. The waterwas completely clear and all the ink remained on the paper.

Spectrophotometry

Cyan density was measured on the blue-printed portions

Given values are an average of 10 measurements.

TABLE 30 Results of spectrophotometric evaluation. Sample Cyan Example11/Printed paper 9 before step A 2.123 Example 11/Printed paper 9 afterstep A 2.007

1. A process for the deinking of coated paper or paperboard, comprisingthe following steps: (i) providing a coated paper or paperboardcomprising, (a) at least one layer consisting of a coating compositioncomprising, (a1) a calcium- or magnesium-exchanged clay, (a2) a binder,(b) at least one layer having a thickness in the range from 0.1 to 10 μmcomprising ink, (ii) activating the calcium- or magnesium-exchanged claybefore or during step (iii) by, (A) carrying out step (iii) with watercomprising monovalent ions selected from the group consisting of sodium,lithium, potassium, ammonium and mixtures thereof, and/or (B) providingin step (i) a binder (a2) that is soluble in water and comprisesmonovalent ions selected from the group consisting of sodium, lithium,potassium, ammonium and mixtures thereof, and/or (C) adding monovalentions selected from the group consisting of sodium, lithium, potassium,ammonium and mixtures thereof in form of a salt before or during step(iii), (iii) treating the coated paper or paperboard as provided in step(i) with water to obtain an aqueous suspension comprising at least ink,clay particles and a paper pulp or a paper residue, wherein layer (a) isdeposited on the paper or paperboard before layer (b).
 2. The processaccording to claim 1, wherein the process comprises a further step (iv)of separating the paper or paperboard from the aqueous suspensionobtained in step (iii).
 3. The process according to claim 1 or 2,wherein the clay is a calcium-exchanged nanoclay selected from the groupconsisting of bentonite, smectite, montmorillonite and mixtures thereofand preferably is bentonite.
 4. The process according to claim 1,wherein the activating step (ii) is, (A) carrying out step (iii) withwater comprising an excess of monovalent ions selected from the groupconsisting of sodium, lithium, potassium, ammonium and mixtures thereofwith respect to calcium or magnesium ions, wherein sodium ions arepreferred and/or (B) providing in step (i) a binder (a2) that is solublein water and comprises monovalent ions selected from the groupconsisting of sodium, lithium, potassium, ammonium and mixtures thereofwith respect to calcium or magnesium ions, wherein sodium ions arepreferred and/or (C) adding sodium ions in form of a salt selected fromthe group consisting of sodium chloride, sodium nitrate, sodiumsulphate, sodium carbonate and mixtures thereof before or during step(iii).
 5. The process according to claim 1, wherein the binder is watersoluble and selected from the group consisting of starch,carboxymethylcellulose, and mixtures thereof and preferably iscarboxymethylcellulose, more preferably the water-soluble bindercomprises an excess of sodium ions with respect to calcium or magnesiumions and/or the coating composition comprises another binder which iswater-dispersible, preferably a latex-binder.
 6. The process accordingto claim 1, wherein the coated paper comprises at least one layer (c)comprising 1 to 30 g/m², preferably from 5 to 20 g/m² and morepreferably 6 to 15 g/m² of a calcium carbonate-comprising material. 7.The process according to claim 6, wherein the calciumcarbonate-comprising material is selected from ground calcium carbonate,precipitated calcium carbonate, surface-modified calcium carbonate, or amixture thereof, and preferably is a natural ground calcium carbonate.8. The process according to claim 6 or 7, wherein the calciumcarbonate-comprising material is selected from natural calcium carbonatesources and preferably is selected from the group consisting of marble,limestone, chalk, dolomite, and mixtures thereof.
 9. The processaccording to claim 1, wherein the thickness of the at least one inklayer is in the range from 0.75 to 5 μm and preferably in the range from0.9 to 2.1 μm.
 10. The process according to claim 1, wherein the waterapplied in step (iii) is selected from the group consisting of tapwater, deionized water and mixtures thereof, preferably is tap water,more preferably is tap water comprising sodium ions, even morepreferably is tap water comprising an excess of sodium ions with respectto calcium or magnesium ions.
 11. The process according to claim 1,wherein mechanical scraping of the surface of the paper or paperboard iscarried out during step (iii).
 12. The process according to claim 1,wherein the content of the calcium- or magnesium-exchanged clay (a1) inthe coating composition, is in the range from 3 to 15 wt.-%, morepreferably 5 to 12 wt.-% and most preferably from 5 to 10 wt.-% based onthe total weight of the coating composition, and/or the coating weightof the at least one layer (a) is from 0.1 to 20 g/m², preferably 1 to 10g/m².
 13. The process according to claim 1, wherein the content of thebinder (a2) in the coating composition is in the range from 0.1 to 12wt.-%, more preferably from 0.2 to 5 wt.-%, even more preferably from0.3 to 2.0 wt.-% and most preferably from 0.5 to 1.5 wt.-% based on thetotal weight of the coating composition.
 14. The process according toclaim 1, wherein the ink in layer (b) is a digital printing ink selectedfrom the group consisting of ink- or dye-based inkjet inks, laserprinting inks and/or toners, offset inks, flexographic inks, rotogravureinks and mixtures thereof.
 15. The process according to claim 1, whereinthe process further comprises the steps of (v) transferring the aqueoussuspensions as obtained in step (iii) or (iv) to a flotation cell,and/or (vi) adding at least one collector agent to the aqueoussuspensions as obtained in step (iii), (iv) or (v), and (vii) passing aflotation gas into the aqueous suspension formed in step (vi) to obtaina phase comprising water and a froth comprising clay and ink, and (viii)separating the froth as obtained in step (vii) from the water.
 16. Theprocess according to claim 15, wherein the at least one collector agentis selected from the group consisting of modified poylethyleneimines,active and hydrophobic tensides, preferably xanthate or thio phosphates,alkyl sulphates, polyalkylenimines, primary amines, tertiary amines,quaternary amines, fatty amines, esterquats, polyesterquats, andimidazolines or quaternary imidazolium compounds, preferably quaternaryimidazolium methosulphates, and most preferred are modifiedpolyethyleneimines.
 17. The process according to claim 15, wherein thecontent of the at least one collector agent is in the range from 0.001to 50 wt.-% based on the total weight of the solids in the aqueoussuspension as provided in step (iii) or (iv), preferably from 0.002 to20 wt.-% based on the total weight of weight of the clay particles andoptional other fillers, more preferably in the range from 0.05 to 0.8wt.-% based on the total weight of the weight of the solids in theaqueous suspension as provided in step (iii) or (iv) and most preferablyin the range from 0.02 to 0.1 wt.-%, based on the total weight of theweight of the solids in the aqueous suspension as provided in step (iii)or (iv).